(US4856965-A)      The control system of pumping operation comprises a cycloconverter for converting AC power from an AC power system into AC power having a given frequency, and an AC exciting generator-motor. The latter has a stator side electrically connected to the AC power system, has a rotor side electrically connected to the cycloconverter, and has a rotor shaft mechanically coupled to a pump-turbine by which the pumping operation is carried out. A circuit breaker is inserted between the AC power system and the AC exciting generator-motor. A rotation speed of the AC exciting generator-motor is controlled so that the rotation speed becomes slow when the pumping operation is to be stopped.    An AC excitation controller decreases a degree of excitation effected by the cycloconverter, wherein decreasing of the excitation degree starts when the rotation speed of the AC excitinggenerator-motor reaches a given minimum value. A circuit breaker controller turns off the circuit breaker when input power, supplied from the AC power system to the AC exciting generator-motor becomes zero.    USE -   Pumped storage power plant. (13pp)    (EP313096-B1)      A control system of pumping operation comprising: power source means (6,7,9), coupled to an AC power system (4,8), for converting AC power from the AC power system (4,8) into AC power having a given frequency; a wound rotor type variable speed AC generator-motor (2), with AC excitation, having a stator electrically connected to said AC power system (4,8), a rotor electrically connected to said power source means (6,7,9), and a rotor shaft mechanically coupled to a pump-turbine (1) by which the pumping operation is carried out; said pump-turbine (1) being provided with a wicket gate (1a) located at a water path (50) of said pump turbine (1); a circuit breaker (3) inserted between said AC power system (4,8) and the stator of said AC generator-motor (2); rotation speed control means (11-13, 100, 103-109), coupled to said AC generator-motor (2) and said power source means (6,7,9), for controlling the rotation speed (N) of said AC generator-motor (2) so as to reduce the rotation speed (N) thereof when the pumping operation is to be stopped; and wicket gate control means (13,16,102), coupled to said wicket gate (1a) and said AC generator-motor (2), to close or squeeze said wicket gate (1a) in response to a reduction in the rotation speed (N) of said AC generator-motor (2); characterised by: AC excitation control means (14,108,109), coupled to said power source means (6,7,9) which excites the rotor of said AC generator-motor (2), for decreasing the degree of the excitation effected by said power source means (6,7,9) when the rotation speed (N) of said AC generator-motor (2), reduced by said rotation speed control means (11-13, 100, 103-109), reaches a predetermined specific value; and circuit breaker off means (11,12,100,101), coupled to said circuit breaker (3) and said AC generator-motor (2), for turning off said circuit breaker (3) when the input power (VG1,IG1), supplied from said AC power system (4,8) to the stator of said AC generator-motor (2), becomes substantially zero.    (DE3873251-G)      A cycloconverter (6) converts AC from a power system (4,8) into AC having a given frequency. An AC exciting generator-motor (2) has its stator connected to the power system and its rotor connected to the cycloconverter and also has its rotor shaft mechanically coupled to a pump turbine (1). A circuit breaker (3) is provided between the AC power system and the generator-motor.    An arrangement (11-13, 100, 103-109) is provided for controlling the rotation speed of the motor such that it turns slowly when pumping is to be stopped. Another controller (14, 108, 109) decreases teh excitation effected by the cycloconverter when the rotation of the motor reaches a minimum value. A circuit breaker controller (11,12,100,101) tur